1. Field of the Invention
The present invention relates to a fuel injection system in an internal combustion engine wherein the amount of fuel to be supplied to the engine is controlled by signals from an air flow meter, for example, having a plate rotatably arranged in the intake pipe of the engine and a potentiometer connected to the plate at its axis of rotation. The present invention is intended to be applied for control of the fuel injection amount when the engine is started.
2. Description of the Related Art
In a fuel injection control system the amount of air introduced into the engine is sensed by an air flow meter, and engine speed is sensed by an engine speed sensor, to obtain a desired ratio Q/N of intake air amount to engine rotational speed. A basic fuel injection period Tp is obtained from Q/N multiplied by a constant Kt, and a final fuel injection period TAU is obtained from the basic fuel injection period Tp to which various corrections are applied in accordance with various requirements of the engine, such as air fuel ratio feedback control, air fuel ratio learning control, enrichment during warming-up control, and the like. Fuel injectors are operated in such a manner that they are opened during the calculated period TAU at a predetermined timing of the engine.
In this type of fuel injection system, an abrupt decrease in engine speed is sometimes generated, causing the engine to stall, even after a full ignition state has been attained for the engine by the operation of a starter. This stalling occurs because of an "undershoot" in the output signal level of the signal from the air flow meter just after the starter is stopped, which undershoot causes the value of the ratio Q/N of intake air amount to engine speed to decrease, and thus the amount of fuel to be injected is also decreased.